Which evolved first, teeth or the jaw? Teeth are used for breaking down food, whereas the jaw is the opposable structure used to grasp prey and food. All living jawed vertebrates have teeth, but it has been understood that the first of these jawed vertebrates lacked those pearly whites. Instead, it was thought that these prehistoric creatures had scissor-like jawbones that were used for capturing prey and eating.

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However, according to new research, these earliest jawed vertebrates possessed teeth too, indicating that teeth evolved along with the evolution of jaws.

Paleontologists from Bristol, the Natural History Museum and Curtin University, Australia collaborated with physicists from Switzerland to study the jaws of a primitive jawed fish called Compagopiscis croucheri.

Because teeth are calcified structures, they are very resistant and can be preserved as shown from the discovery of a 380 million-year-old fish fossil. Researchers were able to use high energy X-rays to reveal the structure and development of the species' teeth and bones.

Lead author, Dr Martin Ruecklin of the University of Bristol said: "We were able to visualise every tissue, cell and growth line within the bony jaws, allowing us to study the development of the jaws and teeth. We could then make comparisons with the embryology of living vertebrates, thus demonstrating that placoderms possessed teeth."

The non-destructive technology showed the developmental stages of how jaws grew and how teeth were added.

Co-author, Professor Philip Donoghue of the University of Bristol's School of Earth Sciences said: "This is solid evidence for the presence of teeth in these first jawed vertebrates and solves the debate on the origin of teeth."

Professor Marco Stampanoni of the Paul Scherrer Institut said: "We performed non-invasive 3D microscopy on the sample using synchrotron radiation, a very powerful X-ray source. This technique allows us to obtain a perfect digital model and very detailed insight views of the old fossil without destroying it. Normally, our method delivers very high spatial resolution on tiny samples. For this experiment we modified our setup and reconstruction algorithms in order to expand the field of view significantly while keeping the spatial resolution high."

Such a discovery not only reveals the evolutionary origin of teeth, but also shows how teeth continue to play a role in both diets and lifestyles.